Remove parens around logger.error params

As requested, I've just removed the parameters to logger.error from within the tuple.

Author: goetzk

djangosaml2/backends.py

@@ -188,7 +188,7 @@ def _get_saml2_user(self, main_attribute, attributes, attribute_mapping):
             user = User.objects.get(**user_query_args)
             user = self.update_user(user, attributes, attribute_mapping)
         except User.DoesNotExist:
-            logger.error('The user "%s" does not exist, searched %s', (main_attribute, django_user_main_attribute))
+            logger.error('The user "%s" does not exist, searched %s', main_attribute, django_user_main_attribute)
             return None
         except MultipleObjectsReturned:
             logger.error("There are more than one user with %s = %s",